The present invention relates to a method of winding yarns, in particular freshly spun or drawn synthetic filament yarns, to form cylindrical cross-wound packages and which involves a stepped precision winding process. In methods of the described type, it is recognized that the yarns advance at a constant speed, so that the package must be driven at a substantially constant circumferential speed.
The stepped precision winding process is known, for example, from Japanese Patent No. 50-65628, which provides that the reversal times are so determined that the winding tension remains within certain limits. At the beginning of a winding cycle, however, the traversing speed drops very quickly, in proportion to the spindle speed, since the diameter of the package increases very rapidly. As a result, the reversal times at which the traversing speed must be reversed from a lower limit value to its upper limit value, follow each other very rapidly.
The same factor applies to the method as described in U.S. Application Ser. No. 838,390, now U.S. Pat. No. 4,697,753. The method there described provides that the traversing speed is reduced first proportionately to the spindle speed between a preset upper limit and a preset lower limit in a recurring sequence of cycles, and then again increased so as to obtain a preset smaller winding ratio, and with the upper and lower limits being decreased or increased in the same sense. In the application of this method it has been found that in all phases of the winding cycle in which the upper limit and the lower limit of the traversing speed are continuously increased, many reversals of the traversing speed closely following each other are necessary. These reversals follow each other particularly closely, when the upper limit and lower limit of the traversing speed are increased at the beginning of a winding cycle. As a result of the necessity to carry out the reversal of the traverse speed very rapidly one after the other in a stepped precision wind, the expenditure for electronic equipment will greatly increase, if the winding ratios (spindle speed: traversing frequency) are maintained with adequate precision, and so as to produce a good package build.
As used in the present application, the traversing frequency and double stroke rate are defined as the number of the traverse cycles per unit of time, with each traverse cycle consisting of one reciprocating motion.
It is accordingly an object of the present invention to provide an improved winding method, particularly for man made filament yarns, wherein the expenditure for circuitry, in particular electronic equipment, may be reduced, and yet a good build of the package remains assured.